On Dec 25, 2007 4:37 PM, Allison Randal <[EMAIL PROTECTED]> wrote:
> Klaas-Jan Stol wrote:
> > I guess you're right :-) I was thinking of ambiguity, like
> >
> > sub foo :multi(Integer, Integer)
> > .param pmc i :invocant
> > .param pmc j
> > .param pmc k :invocant
> > end
> >
> > sub foo :multi (Integer, Integer)
> > .param pmc j :invocant
> > .param pmc k :invocant
> > end
> >
> > but I guess parrot will see that the other foo has 2 parameters while
> the
> > first has 3, and make the selection based on that
>
> Like :optional, the :invocant parameters must all be contiguous. So,
> only the second of those is valid, though you can have as many
> non-:invocant parameters as you like after the last :invocant parameter.
> Also, :invocant parameters can't be :optional.
Earlier I read over this, thinking: there's probably a good reason for that
(the need for being contiguous), but I haven't figured it out yet.
For sake of documentation, could you please explain why this is so?
so, why would it not be possible to write this:
.sub foo :multi
.param pmc x :invocant('Integer')
.param pmc y
.param pmc z :invocant('Integer')
...
and
.sub foo :multi
.param pmc x :invocant('Integer')
.param pmc y
.param pmc z :invocant('String')
The former "foo" can be thought of as having signature "Integer, *, Integer"
and the second "Integer, *, String", (where * means any type, don't care).
I don't see a particular problem. Not that I need to be able to do this,
just wondering why this rule is so.
thanks,
kjs
>
>
> > BTW, :invocant looks a bit like ".invcant", which is also a directive.
> Can
> > that confuse people?
>
> Do you mean ".invocant"? They are related concepts, as .invocant sets
> the single invocant of a method call, while :invocant tells a
> multisub/method to treat a set of parameters as invocants. Any .sub
> marked with :method and :multi always treats the method invocant as if
> it was marked with :invocant, even though it isn't retrieved with .param.
>
> We might want to consider adding a standard prefix to .invocant, as well
> as to .arg, .result, etc, to make it clear that they're a group of
> directives all combined to make a single PCC call.
>
> Allison
>
